This invention relates to a multishaft supporting device for use in a kneading machine, a twin shaft extruder or the like.
A plurality of screw shafts of these machines have been supported by a barrel having a sleeve formed with a plurality of openings for supporting the screw shafts. The sleeve has generally a figure 8 shaped opening for supporting two screw shafts and made of wear resistant and corrosion resistant material. According to prior art constructions, the barrel and the sleeve are divided into upper and lower sections along a horizontal plane and the upper and lower sections are bolted together or the sleeve is bolted to the inner surface of the barrel. According to these constructions, however, in order to improve the heat transfer between the inner surface of the bore of the barrel and the peripheral surface of the sleeve it is necessary to finish these surfaces at high accuracies to minimize, as far as possible, the gap therebetween. This not only requires a high degree of machining but also is impossible to decrease heat loss. According to another prior art construction, molten metal having low melting point is poured into the gap between a barrel and a sleeve contained therein to integrally combine the barrel and the sleeve. With this construction, however, when the temperature of the barrel increases beyond the melting point of the metal during the use of the barrel, the metal would melt to release the sleeve from the barrel. This construction also requires to carefully machine such that the gap between the inner bore of the barrel and the outer periphery of the sleeve would be uniform. Moreover, when pouring the molten metal into the gap, it is necessary to hold the barrel and the sleeve to maintain uniform gap.
As a wear resistant material, metal carbides, for example, sintered tungsten carbide have been used, but such metal carbides have low thermal expansion coefficients and small elongations at the time of fracture so that when they are used to form a sleeve, a gap or stress would be formed due to the difference between the thermal expansion coefficients of the barrel and the sleeve.